//	ID : pallab81
// 	PROG : 11408
// 	LANG : C++
// 	2011-09-09-16.05.00 Friday
//
// 	"I have not failed, I have just found 10000 ways that won't work.
//


#include <iostream>
#include <algorithm>
#include <vector>
#include <sstream>
#include <fstream>
#include <string>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <functional>
#include <bitset>

#include <ctime>
#include <cassert>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <climits>
#include <cstring>
#include <cstdlib>

using namespace std;

#define VI vector< int >
#define CI( x ) scanf("%d",&x)
#define CL( x ) scanf("%lld",&x)
#define CD( x ) scanf("%lf",&x )
#define fo(i,st,ed) for(int i = st ; i < ed ; ++i )
#define foE(i,st,ed) for(int i = st ; i <= ed ; ++i )
#define foit(i, x) for (typeof((x).begin()) i = (x).begin(); i != (x).end(); i++)
#define bip system("pause")
#define Int long long
#define pb push_back
#define SZ(X) (int)(X).size()
#define LN(X) (int)(X).length()
#define mk make_pair
#define f first
#define s second
#define SET( ARRAY , VALUE ) memset( ARRAY , VALUE , sizeof(ARRAY) )

inline void wait( double seconds ){
    double endtime = clock()+( seconds* CLOCKS_PER_SEC );
    while( clock() < endtime ){
        ;
    }
}
const int inf=5000000;
int good[ inf+10 ];
int dePrimes[ inf+10 ];
int primes[inf+10];
int st,ed;

inline bool isPrime(int x){
    if( x<2 )return false;
    if( x==2 )return true;
    return ( (x&1)!=0 && good[x]!=0 );
}

inline void sieve(){
    SET(good,-1);
    int sqrtN = (int)sqrt( (double)inf );
    for(int i=3;i<=sqrtN;i+=2){
        if( good[i]!=0 ){
            for(int j=i*i ; j<inf; j+=i ){
                good[j]=0;
            }
        }
    }
}
inline void gen(){
    SET(primes,0);
    for(int i=2; i<=inf; ++i){
        if(isPrime(i)){
            for(int j=i; j<=inf; j+=i ){
                primes[j]+=i;
            }
        }
    }
}
inline bool DePrime(int n){
    int var = primes[n];
    return isPrime(var);
}
inline void store(){
    int total=0;
    for(int i=0;i<=inf;++i){
        if( DePrime(i) ){
            ++total;
        }
        dePrimes[i]=total;
    }
}
int main(){
//    #ifndef ONLINE_JUDGE
//        freopen("in.txt","rt",stdin);
//    #endif
    sieve();
    gen();
    store();
    while( scanf("%d",&st)==1 && st!=0 ){
        CI(ed);
        cout<<dePrimes[ed]-dePrimes[st-1]<<"\n";
    }

return 0;
}
